Cesium Iodide

Cesium iodide powder is a colourless or white crystalline powder, toxic and light-sensitive, easily deliquescent, thermally stable, easily soluble in water and alcohols, widely used in infrared spectrometer prisms, X-ray detectors, scintillation counters and other fields.

Properties

Appearance: usually colourless crystal or white powder.

Density: Relative density is 4.51 g/cm³.

Melting point: 621°C

Boiling point: 1280°C

Solubility: Cesium iodide is soluble in water (44g/100ml at 0℃, 74g/100ml at 20℃) and alcohols. Solubility in water is 848g/L at 25℃.

Refractive index: The refractive index varies at different wavelengths, e.g., 1.9790 at 0.3 µm, 1.7873 at 0.59 µm, 1.7694 at 0.75 µm, 1.7576 at 1 µm, 1.7428 at 5 µm, 1.7280 at 20 µm.

Flame reaction: Burning on a flame gives a sky-blue flame colour.

Crystal structure: caesium iodide has the crystal form of caesium chloride (cscl, cp2).

Stability: strong thermal stability, but easily oxidised by oxygen in humid air.

Reactivity: can be oxidised by strong oxidising agents such as sodium hypochlorite, sodium bismuthate, nitric acid, permanganate, chlorine; can react with silver nitrate to produce a yellow insoluble silver iodide precipitate (CsI + AgNO₃ = CsNO₃ + AgI↓); and can react with iodine to produce stable cesium triiodide (CsI + I₂ → CsI₃).

Other properties: easily deliquescent, sensitive to light.

Applications

Medical field:

X-ray detectors: Cesium iodide is used as a scintillation crystal in digital X-ray detectors. It can convert X-rays into fluorescent signals, which are then converted into electrical signals by photodiodes, and is characterised by high scintillation efficiency, high spatial resolution and high spectral sensitivity. Compared with other materials, X-ray detectors using caesium iodide require lower X-ray doses and are relatively safer, making them widely used in medical imaging.

X-ray image intensifier tubes: used as input phosphors to enhance the brightness and clarity of X-ray images, helping doctors diagnose diseases more accurately.

Scientific research:

Particle physics experiments: It is one of the scintillator materials for electromagnetic quantum energiser. In particle physics experiments, it is used to detect and measure the energy of high-energy particles.

Infrared spectral analysis: it can be used to manufacture prisms and spectroscopes for infrared spectrometers. Compared with the commonly used potassium bromide spectroscope, cesium iodide has a wider range of light transmission that extends into the far infrared.

Analytical reagent: used as a reagent in chemical analysis to detect and analyse other substances.

Industrial field:

Additives for special electric light sources: added to special electric light sources to improve the performance and spectral characteristics of the light sources.

Special optical glass: used in the manufacture of special optical glass to improve the optical properties and weather resistance of the glass